void Inkscape::LineSnapper::constrainedSnap(SnappedConstraints &sc,
Inkscape::SnapCandidatePoint const &p,
Geom::OptRect const &/*bbox_to_snap*/,
ConstraintLine const &c,
std::vector<SPItem const *> const */*it*/) const
{
if (_snap_enabled == false || _snapmanager->snapprefs.getSnapFrom(p.getSourceType()) == false) {
return;
}
/* Get the lines that we will try to snap to */
const LineList lines = _getSnapLines(p.getPoint());
for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
if (Geom::L2(c.getDirection()) > 0) { // Can't do a constrained snap without a constraint
// constraint line
Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : p.getPoint();
Geom::Line line1(point_on_line, point_on_line + c.getDirection());
// grid/guide line
Geom::Point const p1 = i->second; // point at guide/grid line
Geom::Point const p2 = p1 + Geom::rot90(i->first); // 2nd point at guide/grid line
Geom::Line line2(p1, p2);
Geom::OptCrossing inters = Geom::OptCrossing(); // empty by default
try
{
inters = Geom::intersection(line1, line2);
}
catch (Geom::InfiniteSolutions e)
{
// We're probably dealing with parallel lines, so snapping doesn't make any sense here
continue; // jump to the next iterator in the for-loop
}
if (inters) {
Geom::Point t = line1.pointAt((*inters).ta);
const Geom::Coord dist = Geom::L2(t - p.getPoint());
if (dist < getSnapperTolerance()) {
// When doing a constrained snap, we're already at an intersection.
// This snappoint is therefore fully constrained, so there's no need
// to look for additional intersections; just return the snapped point
// and forget about the line
_addSnappedPoint(sc, t, dist, p.getSourceType(), p.getSourceNum(), true);
// For any line that's within range, we will also look at it's "point on line" p1. For guides
// this point coincides with its origin; for grids this is of no use, but we cannot
// discern between grids and guides here
Geom::Coord const dist_p1 = Geom::L2(p1 - p.getPoint());
if (dist_p1 < getSnapperTolerance()) {
_addSnappedLinesOrigin(sc, p1, dist_p1, p.getSourceType(), p.getSourceNum(), true);
// Only relevant for guides; grids don't have an origin per line
// Therefore _addSnappedLinesOrigin() will only be implemented for guides
}
}
}
}
}
}
void Inkscape::LineSnapper::constrainedSnap(SnappedConstraints &sc,
Inkscape::SnapPreferences::PointType const &t,
Geom::Point const &p,
bool const &/*f*/,
Geom::OptRect const &/*bbox_to_snap*/,
ConstraintLine const &c,
std::vector<SPItem const *> const */*it*/) const
{
if (_snap_enabled == false || _snapmanager->snapprefs.getSnapFrom(t) == false) {
return;
}
/* Get the lines that we will try to snap to */
const LineList lines = _getSnapLines(p);
for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
if (Geom::L2(c.getDirection()) > 0) { // Can't do a constrained snap without a constraint
/* Normal to the line we're trying to snap along */
Geom::Point const n(Geom::rot90(Geom::unit_vector(c.getDirection())));
Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : p;
/* Constant term of the line we're trying to snap along */
Geom::Coord const q0 = dot(n, point_on_line);
/* Constant term of the grid or guide line */
Geom::Coord const q1 = dot(i->first, i->second);
/* Try to intersect this line with the target line */
Geom::Point t_2geom(NR_HUGE, NR_HUGE);
Geom::IntersectorKind const k = Geom::line_intersection(n, q0, i->first, q1, t_2geom);
Geom::Point t(t_2geom);
if (k == Geom::intersects) {
const Geom::Coord dist = L2(t - p);
if (dist < getSnapperTolerance()) {
// When doing a constrained snap, we're already at an intersection.
// This snappoint is therefore fully constrained, so there's no need
// to look for additional intersections; just return the snapped point
// and forget about the line
sc.points.push_back(SnappedPoint(t, Inkscape::SNAPTARGET_UNDEFINED, dist, getSnapperTolerance(), getSnapperAlwaysSnap(), true));
// The type of the snap target is yet undefined, as we cannot tell whether
// we're snapping to grid or the guide lines; must be set by on a higher level
}
}
}
}
}